std::unique_ptr<PolyProtoAccessChain> PolyProtoAccessChain::create(JSGlobalObject* globalObject, JSCell* base, JSObject* target, bool& usesPolyProto)
    JSCell* current = base;
    VM& vm = *base->vm();

    bool found = false;

    usesPolyProto = false;

    std::unique_ptr<PolyProtoAccessChain> result(new PolyProtoAccessChain());

    for (unsigned iterationNumber = 0; true; ++iterationNumber) {
        Structure* structure = current->structure(vm);

        if (!structure->propertyAccessesAreCacheable())
            return nullptr;

        if (structure->isProxy())
            return nullptr;

        if (structure->isDictionary()) {
            if (structure->hasBeenFlattenedBefore())
                return nullptr;

            structure->flattenDictionaryStructure(vm, asObject(current));

        // To save memory, we don't include the base in the chain. We let
        // AccessCase provide the base to us as needed.
        if (iterationNumber)
            RELEASE_ASSERT(current == base);

        if (current == target) {
            found = true;

        // We only have poly proto if we need to access our prototype via
        // the poly proto protocol. If the slot base is the only poly proto
        // thing in the chain, and we have a cache hit on it, then we're not
        // poly proto.
        usesPolyProto |= structure->hasPolyProto();

        JSValue prototype = structure->prototypeForLookup(globalObject, current);
        if (prototype.isNull())
        current = asObject(prototype);

    if (!found && !!target)
        return nullptr;

    return result;